Men who have sex with men (MSM) and use the Internet for social and sexual networking have been identified as at increased risk for HIV. Although HIV prevention outreach and intervention delivery is being done online, evaluations of these interventions tend to emphasize process (not outcomes), focus on hypothesized predictors of change (versus behavior change), and are challenged by high attrition rates and/or short follow-up. In response to PA-08-074 Community Participation in Research, which promotes intervention research that communities and researchers jointly conduct, our community-based participatory research (CBPR) partnership proposes a 4-year study (R01) to refine, implement, and evaluate a culturally congruent chat room intervention designed to increase HIV testing among MSM. The intervention is entitled CyBER/testing; is based on social cognitive theory and theory of empowerment education; and increased HIV testing rates during a proof-of-concept study. A total of 4 chat rooms that represent 4 geographically distinct catchment areas in NC have been paired and matched based on catchment area sizes. From each matched pair, 1 chat room will be randomized to intervention and the other chat room to delayed intervention. Cross-sectional data will be collected and extant profile data will be abstracted from chat room MSM at (1) baseline, (2) immediate post intervention, and (3) 12-month follow-up. This is an intent-to-treat study, in which participant data will be analyzed based on randomization group. Our hypothesis is that those in the intervention, relative to peers in the delayed-intervention comparison group, will have a higher rate of self-reported HIV testing at immediate post-intervention. Qualitative data also will be collected using (1) focus groups with chat room MSM who report having seen the interventionists in the chat rooms, and (2) individual in-depth interviews with MSM who report having talked with an interventionist in the chat rooms and having been tested for HIV. We also will evaluate the CBPR process, using direct observation of partnership meetings and individual in-depth interviews with partners. This study will advance the field of HIV prevention research and fill existing gaps in knowledge in 3 important ways: (1) refining and making available a culturally congruent chat room intervention to increase HIV testing among MSM, ready for further implementation, adaptation to other online modalities and social media, and testing; (2) promoting a deeper understanding of HIV testing behavior among MSM who use Internet chat rooms; and (3) elucidating an HIV prevention research partnership process that includes lay community members, AIDS service organizations, community-based organizations, multiple universities, and an expanding broad spectrum of geographically dispersed partners.